With the rapid development of the recent digital information society, an increase in the capacity has been required in an optical disk, which is one of representative storage devices, and intense development has been advancing in many fields. A φ120 mm optical disk which is now commercially available has a pit length of 0.1 μm to 0.2 μm and a capacity from about 15 GB to 30 GB. A technology has now been considered to increase the capacity by reducing the shortest pit length in the next generation and the next generation. In order to achieve this, an original disk has been manufactured by the Deep UV laser beams or electron beams. Reported is a technique of forming an extremely short pit such as the shortest pit length of 80 nm manufactured by the Deep UV laser beams and the shortest pit length of about 40 nm manufactured by the electron beams. When the shortest pit length is about 40 nm, the capacity is estimated to be about 500 GB/12 cm.
An optical disk substrate used for such high-density recording/reproducing is manufactured by an injection molding method using a stamper on which a replicated pattern is transferred from the original disk of the optical disk described above (see patent literatures 1 to 3).
Another method for achieving an increase in the capacity is forming an information recording layer on an asperity pattern on the optical disk substrate described above. Then, the second asperity pattern is arranged using the ultraviolet curable resin. After forming a film on this asperity pattern, a third asperity pattern is further provided using an ultraviolet curable resin, so as to form a film. By repeating these processes, the optical information recording medium that includes a plurality of information recording layers can be obtained.
Further method for achieving an increase in the capacity is to store in one cartridge a plurality of multi-layer optical disk media each including a plurality of information recording layers as described above. In this way, the increase in the capacity of the optical disk system is intended to be achieved.